@article{H_hnle_1994,
    doi = {10.1007/bf00881956},
    url = {https://doi.org/10.1007%2Fbf00881956},
    year = {1994},
    publisher = {Springer Science and Business Media {LLC}},
    volume = {13},
    number = {2},
    pages = {211--221},
    author = {Reiner H\"ahnle and Peter H. Schmitt},
    title = {The liberalized ?-rule in free variable semantic tableaux},
    journal = {Journal of Automated Reasoning}
}

@article{H_hnle_1994, doi = {10.1007/bf00881956}, url = {https://doi.org/10.1007%2Fbf00881956}, year = {1994}, publisher = {Springer Science and Business Media {LLC}}, volume = {13}, number = {2}, pages = {211--221}, author = {Reiner H\"ahnle and Peter H. Schmitt}, title = {The liberalized ?-rule in free variable semantic tableaux}, journal = {Journal of Automated Reasoning} }